Scheduling Aperiodic and Sporadic Tasks in Hard Real-Time Systems
Scheduling Aperiodic and Sporadic Tasks in Hard Real-Time Systems
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Date
1998-10-15
Authors
Choi, Seonho
Agrawala, Ashok K.
Advisor
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Abstract
The stringent timing constraints as well as the functional correctness
are essential requirements of hard real-time systems. In such systems,
scheduling plays a very important role in satisfying these constraints.
The priority based scheduling schemes have been used commonly
due to the simplicity of the scheduling algorithm. However, in the presence
of task interdependencies and complex timing constraints, such
scheduling schemes may not be appropriate due to the lack
of an efficient mechanism to schedule them and to
carry out the schedulability analysis. In contrast,
the time based scheduling scheme may be used to schedule a set of tasks
with greater degree of schedulability
achieved at a cost of higher complexity of off-line scheduling.
One of the drawbacks of currently available scheduling schemes,
however, is known to be their
inflexibility in dynamic environments where dynamic processes
exist, such as aperiodic and sporadic processes.
We develop and analyze scheduling schemes which efficiently provide
the flexibility required in real-time systems
for scheduling processes arriving dynamically.
This enables static hard periodic processes and dynamic processes(aperiodic
or sporadic) to be jointly scheduled.
(Also cross-referenced as UMIACS-TR-97-44)